Weight sensing device



9 merits-being connected adjacent their lower ends to 'sa-id load carrying; member; and a loadrespgnsive device seou'redto said support mem-' face of said transverse opening whereby the load carried by said load-carrying member will-be imposed" upon said load-responsive device, said beam element. being adapted, upon structural failure'of said load-responsive device, to be supportedbythe lower surface of saidtransverse opening independently of said device.

'5. A swivel bail adapter comprising: a shank member adapted for supporting encirclement by a wellpipeelevator, said member having a transverse opening and a longitudinal bore formed therebelow and intersecting said opening; a swivel bail-supporting saddle member; a pair of spaced side plates connected adjacent their upper ends .by a pin. supported within said shank opening'and connected adjacent their lower ends to said saddle member; and a load-responsive capsule detachably secured to the lower portionof said shank member, said capsule having a first portion upon which are mounted bonded wire resistance elements for sensing a load imposed upon said capsuleand having a second portion disposed within said shank bore to normally maintain. said pin in awn-supported relationto the. lower -.surface of said shankopening whereby the load suspended from said saddle member will be imposed upon said'load-responsive capsule, said pin being adapted, upon structural failure of said capsule, to be supported by the lower surface of said shank opening independently of said capsule.

6. A swivel bail adapter comprising: a shank member adapted for supporting encirclement by an elevator; a saddle member adapted to sustain a swivel bail'and being formed with a pair of lateral extensions; a pair of spaced side plates connected adjacent their upper ends to said shank member, each of said plates having a lateral opening formed adjacent its lower end adapted to receive one of said saddle extensions and having a longitudinal bore formed therebelow intersecting said lateral opening; and a pair of load-responsive capsules, each being secured to the lower portion of a respective side plate and having a first portion disposed within the respective bores in said side plates to normally maintain said saddle extensions spaced from the lower surfaces of the side plate openings whereby the load suspended from said saddle member is imposed upon said capsules, said capsules incorporating a second portion on which are mounted bonded wire resistance'elements for sensing said load, said extensions being adapted, upon structural failure of said capsules, to engage the lower surfaces of said side plate openings and thereby transfer the load directly therebetween independently of said capsules.

7. Load supporting and sensing apparatus comprising: a support member having a transverse opening; a load-carrying member; a pair of spaced tension elements connected adjacent their upper ends to said support member by a beam element supported within said opening; and a load-responsive device interposed between said support member and said tension elements to normally maintain said beam element spaced from the'lowersurface of said transverse opening and thereby assume the load carried by said load-carrying member, said device mounting bonded wire resistance elements for sensing said load, said beam element being-adapted, upon a structuralfailure of said load-responsive device,

to engage the lowersurface of said transverse opening, so as-to transfer said lead directly therebetween independentlyof said device.

8. A swivel bail adapter comprising: a shank member adapted for supporting encirclement by an elevatonsaid shank member having a transverse opening; a swivel bail supporting-saddle member; a pair of spaced side platesconnected adjacent their upper ends by a pin supported within said shankopening and connected adjacent their lower ends tosaid saddle member;

and a load-sensitive tension link secured adjacent-itsupper end-to said shank member and secured adjacent its lower end to said side plates so:as to= normally maintain said pin spaced from the lower surface ofisaid shank opening whereby saiddoad-sensitive tension link is subjected to strain proportional to the load' suspended from said saddle: member, said link mounting bonded- Wire resistance elements for sensing said load, and said pini bein adapted, upon structural failureof said link, to engage the lower. surface of said shank opening to thereby transfer said load directly therebetween independently of said link.

9. Load supporting and sensing apparatus comprising:: a support member; a load-carrying member; an intermediate load-transferringmember comprising a pair ofspaced tension elementsand-a beam element, said tension elements being connectedadjacent their upper ends to said supDQrtmember-by said beam element and being connected adjacentthe. lower ends to said loadcarrying member; and a load sensitive deviceoperatively interposed'in load-sustainin relation between saidiload-transferring member and one of the other; members, said load sensitive device having bonded wire resistance elements mounted on a portion thereof ,forsensing the load sustained by said device, said load transferring member and said one other member having complementary load-bearing surfaces normally maintained spaced apart by said load sensitive device whereby said device is subjected to strain proportional to a load carried by said load-carrying member, said load-bearing surfaces being member adapted to be encircled and supported by a well pipe elevator; a swivel bail supporting member; an intermediate load-transferring member, said member being connected at its upper end to said shank member and at its lower end to said swivel bail supporting member; and a load-sensitive device operatively interposed in load-sustaining relation between said load-transferring member and one of the other members, said load-sensitive device having bonded Wire resistance elements mounted on a portion thereof for sensing the load sustained by said device, said load-transferring member and said one other member having complementary load-bearing surfaces normally maintained spaced apart by said load-sensitive device whereby said device is subjected to strain proportional to a load supported by said swivel bail supporting member, said load- July 14, 1953 L. B. SCOTT WEIGHT SENSING DEVICE 4 Sheets-Sheet 1 Filed April 29, 1949 LVLE 5. 56077; INVENTOR.

BY I

July 14, 1953 B. SCOTT 2,645,121

WEIGHT SENSING DEVICE Filed April 29, 1949 4' heets-Sheet 2 v LVLE 5. 56077; INVENTOR.

afie. I 60 BY July 14, 1953 Filed April 29, 1949 L. B. SCOTT WEIGHT SENSING DEVICE 4 Sheets-Sheet 4 045 e. scorr,

INVENTOR.

HTTOQNE'VS tion up Patented July 14, 1953 UNIT o sTATss PATENT OFFICE .WEIGIYIT-SENSING DEVICE Lyle B.Scott, South Gate, Califi, assignor to Byron Jackson 00., Vernon, Calif., a. corporation of Delaware Applic-ation April29, 1949, SerialNo. 90,414

' 13 Claims.

This invention relates generally to weight sensing devices, and particularly to an improved weilght sensing device for use in the drilling of oil we s. l

In the drilling of an oil we1l,-it frequently becomes necessary that the operator be informed as toweights, line tensions, and the like. For example, where drilling with rotary equipment wherein a heavy drill string is used to suspend the drill bit; in order to insure the efficient cutting of 1 the formation, in order to avoid damage to the drillingapparatus, and in order to minimize the possibility of a crooked hole, it is desirable that the pressure of the drill bit against the formation be closely regulated. Since the weight 'ofthe entire drill string imparts a pressure greater than can be used advantageously or even safely under usual conditions, part of the weight. of the said drillstring mustbesuspended, and it is desirable to know just what part of said weight is suspended in order to determine the pressure on the drill bit;

The drill string is suspended from a drilling cable, and there have heretobefore been provided weight indicators which provide a reading as to the weight beingsuspended. Themost cormnon type of such a weight indicator operates on the principle of misaligning a portion of the station-v ary end of the drilling cable or dead line so that the load tends to straighten out the misaligned portion.

dieating device which converts the force into sensible indicationsby hydraulic or mechanical means connected within the weight indicator'device itself, Such indications appear upon an indicator dial attached directly to the body of the device or appear upon a dial adjacent the drllers position. I V In the hydraulic type Weight indicator previously mentioned there is .usually provided a closed fluid system within which a diaphragm is. so flexed by the force of the deflected drilling cable as to impose a pressure upon the fluid which This tendency to straighten out the cable is used to transmit a force to the weight in- 2 is subject to an appreciable vibration and the instrument is therefore often difficult to read, particularly when the deadline is located at some distance from the position of the driller. Further, the hydraulic-type previously described lacks in accuracy due to temperature changes and leakage, and it is frequently necessary to interrupt drilling operations in order to perform readjustments to'avoid the said inaccuracies. As to the mechanical type indicator, particularly serious inaccuracies arise from the vibration of the deadline, in large part due to the frequent positioning of the indicator dial on the instrument itself.

Further, it is inherent in the nature of the mechanical type weight indicator that a low order of sensitivity is present and that time lag therein is excessive.

In the present invention it is proposed to provide aweight indicator neither dependent-upon mechanical linkage nor, upon fluid pressures.

Such a device is made possible in view of the invention disclosed in Patent No. 2,292,549, entitled Material Testing. Apparatus, issued August 11,

' 1942, to E. E. Simmons, Jr., which consists'in a means for measuring forces and weights comprising bondedwire resistance strain gauges. Such means makesuse of the fact that the resistance of a conductor will vary as a function of a strainimparting force applied to the conductor. Y

However, the difficulties attendant upon application of the aforesaid invention to the oil well weight indicating art are manifest. For example,

' since the sensible accuracy of devices of this kind depends upon variation in resistance responsive to strain, it is obvious that the strain gauges should be bonded to a load responsive member to which considerable strain isimparted as the result of a given force. Such load responsive member must therefore be of small cross-section but on the-other hand such load responsive member;

being of small cross-section, must not be in a position whereby the possibility'of failure in the member might decrease the safety factors necessaryto the entire drilling operation. 7

Again, since the accuracy of such type device is dependent upon the transmission of a uniform' strain to the bonded conductors, the organization of any weight sensing device embodying these strain gauges must be such that any straining of the conductors therein is in fact uniform. Moreover, the nature of the strain gauge itself requires that it be protected, that it be not subject to blows, moisture, or the deleterious effects of the corrosive substancesfrequently found in proximity to oil well operations. I I T It is therefore the principal object of this invention to provide a novel means for accurately measuring and instantaneously indicating weights, forces and the like in the oil well drilling art.

Another principal object of this invention is to provide a weight sensing device including bonded wire resistance strain gauges.

A further object is to provide such a weight sensing device wherein the safety'of the drilling operation is not adversely affected by the presence of such bonded wire resistance strain gauges.

And yet another object is to provide a weight sensing device embodying bonded Wire resistance strain gauges wherein the conductors of such strain gauges are invariably subjected to uniform strain.

And it is a general object of this'invention to provide a new load measuring device of the type operable from a misaligned portion of a fiexible element such as a drilling cable, the accuracy of which is not adversely affected by temperature variations'or by vibration, the sensible indications of which may be read 'on a dial remote from the device itself and easily accessible to the driller and which is substantially free of any lag whatsoever between the time of receivin a force change and the time of sensibly indicating such force change on the dial. I

Further objects of the invention will appear hereinafter.

In the drawings:

Figure 1 is aschematic View in side elevation of a derrick in which a weight sensing device built in accordance with this invention has been installed;

Figure 2 is a side elevational view of said weight sensing device;

Figure 3 is a front elevational View thereof;

Figure 4:- is a rear elevational view of saidrdcvice;

Figure 5 is an enlarged longitudinal sectional view of the weight sensing device;

Figure 6 is an enlarged partial View of such device partly in section;

Figure '7 is a perspective view of one bonded wire resistancestrain gauges;

Figure 8 is a wiring diagram showing the znanner in which the bonded wire resistance strain gauges are electricallyconnected; and

of the Figure 9 is a viewsimilar to Figure 5 but-showinga modificationthereof.

Referring to the drawings, Figure 1 shows a conventional oil well drilling apparatus wherein a drill string 29 carrying a drill bit (not shown) is supported by a rotary swivel 22 which is in turn carried by a connector 24 supported by a traveling block 26. Drilling cable 28 passes from a draw works 39 over a crown block 32 in the top of the derrick 34 through sheaves in the trave ing block 2'6 back over the said crown block 32 and to an anchor 36. The portion of the drilling cable 28 extending from the crown block 32 to the anchor 35 is known as the deadline and it is to this portion of the drilling cable that the weight sensing device 38 embodying'one form of the instant invention is connected, preferably at a point adjacent to the anchor 36. A conductor cable 40 leads from the weight sensing device 38 to a dial instrument 42 located near the drillers position wherein the output of the device is indicated and wherein such output may be recorded.

Referring to Figures 2 through 5 inclusive, and particularly to Figure 5, a weight sensing device constituting one embodiment of this invention broadly comprises a frame 44 suspended from the derrick floor 46 by an eye 48, a connecting roller 59, a clamp 52, and a load transmitting member or plunger 54 abutting the cable 28 and operatively connected to the bonded wire resistance sensing elements 59 and 59 which are mounted on a load-responsive structure which, in the embodiment shown, is in the form of a cylindrical sleeve H9. Conductor wires are connected to the elements 58 and 59 and lead through the conduit 49 to the dial instrument 42. By virtue of this device, upon the application of a load to the drilling cable 28, such cable tends to straighten and'applies a linear compressive force to the load-transmitting member or plunger 54, which force subjects the loadresponsive member H9 to tensile strain, producing a corresponding strain in the elements 58 and 59, varying the resistance thereof, the said load being read on the dial instrument 42. It will thus be seen that the assembly embodying this invention is not interposed in the path of the load being supported by the drilling cable 28 and that no failure thereof could affect the effective support of the load by the said cable 28.

In the particular construction of device shown in Figures 2 to- 5 inclusive, the frame 44 is provided with webbing 64 and supports a main body 69. Said main body 66 is provided with a threaded bore 68 and counterbore ill to receive the strain gauge assembly which will hereinafter be described and which is generally indicated as 12. At the upper extremity of the frame the eye 48 is threadedly received in a boss 14 and there extends from said frame 44 a bifurcated extension "iii which carries rotatably a pin it upon which-the cable engaging roller 59 rotates. Cotter-pins 8i? may be used to hold the pin 18 in place.

At the other extremity of the frame 44 there is provided an extended boss 82 having a bore 84 through which extends a pin 86' carrying the clamp 52. Such pin 86 is provided with a threaded extremity 98 onto which is threaded a sleeve 90 carrying a shoulder 92 and having a handle 94. Thus when the handle 94 is turned, the sleeve 99, Whose shoulder 92 abuts the boss 82, moves the pin 86 to draw the clamp 52 against the cable 28.

The plunger 54, as shown in Figure 5, comprises a saddle 96 abutting the deflected portion of the cable 28, and also includesa shank 98. The shank 98 is a portion of the strain gauge assembly 12 and has a grooved extremity I00 inserted in a socket 102 in the saddle fitand held therein by the transverse pin Hi4. It has another extremity lllfi which is threaded into the bore 18 of a cylindrical sleeve H9. The sleeve is provided with a threaded extremity H2 threaded into the threaded bore 68 of the main body 65. It further is provided with a reduced shank portion H4 upon'which are mounted the bonded wire resistance elements 59 and 59.

The electrical circuit of the strain gauges assembly is shown in Figure 8 and is in the form of a Wheatstone bridge. Elements 58, as best shown in Figure 6, are bonded apart on the circumference of reduced shank H4 of the sleeve H0 with their filament parallel to the axis of the plunger shank 98. On the other hand, elements 59 are bonded to said reduced shank H4 180 apart but in a circumferential path with'their'filaments perpendicular to those of the elements 58. Hence when a load is apby virtue of the connection of the shank 98' with the sleeve III] and of thesleeve III] with the main body 66, is converted to tension in the said sleeve lit and a tensile strain is imparted to the reduced shank portion 'I I4 of said sleeve. This strain resultslin a lengthening of the filament in the elements 58 and a conse-:

- quent increase'in their resistance. Correspondthe potentiometer branch of the Wheatstone motor conbridge to energize a null balance nected to the dial pointer.

It will of course be apparent that it would be possible to directly bond the respective elements 58 and 59 to the shank 98 of the plunger 54. However, it will be noted that such shank is always in compression and it has been found that it is exceedingly difiicult to impart a uniform strain to a member under compression and hence a uniform strain to elements bonded to such member. I have, however, discovered that the elements need not be bonded directly to such r a member'under compression, but that such compression can be converted to tension by the addition of a tensioned member in proper combination and -the.elements bonded directly to such tensioned member. Such expedient has been i found not only to result in a transfer of a uniform strain to the respective elements,-. but also enables the use of an element carrying member of even less cross-section than would be otherwise necessary. This is because the compression problem of buckling is not present in a member under tension and results in a more strain-responsive assembly and consequently a moresensitive indicator.

In order to protect the respective elements from oil. water, andmechanical damage, a, protective layer of rubber H6 is bondedto the reduced shank I I4. In order to assure free relative movement between the shank 98 of the plungertt and the reduced shank II4 of the sleeve lit, the annular space IIB therebetween is filled with oil, grease or other lubricating sub.- stance. An oil seal I and retainer bushing I22 are provided to seal said oil within such annular space and to exclude moisture and the like from such space; Finally, a hanger I24 which supports a. rubber grommet I 26 is supported by the head I28 of the'sleeve III). Such grommet carries the conduit 62 leading to the indicator dial In the installation and operation of the abovedescri-bed embodiment of the invention it is only necessary to remove one of the cotterpinstiil, slide the pin I8 transversely so that the roller 50 may be removed and place the drilling cable 28 between .the bifurcated ends 16, at the same time laying said cable over the saddle 96 of the plunger 54 andplacing it between the clamp 52 and the boss .82. The roller may then be replaced and the handle -94 turned in the proper direction to clamp the said cable 28. Loading of the drilling cable 28 will result in an application of a force to the plunger 54; Such force is compressive butis transferred to the sleeve I ID. A tensile strain is produced in the reduced portion II4 of said sleeve and is imparted to the filaments of the respective elements. Such strain results in resistance Variation in. the strain gauge assembly and such resistance variation appears on the dial of the indicator instrument 42 in terms of weight units. 7

It will be notedthat the weight sensing device hereinabove described has noefiect whatsoever on the safety factor present in the drilling rig itself, no member of the said device carrying any part of a suspended load. It will .be further noted that no strain gaugemeasurement arises as'the result of compression of a member carrying the device. Thus the strain in all elements is proportional to the force exerted as the result of the deflection of the cable 28 and is-proportional to the load suspended from the cable 28.

In Figure 9 there is shown a slightly modified form of the invention, incorporating all of the advantageous features of the previously described embodiment. Whereas in the previously described embodiment the cable or other flexible element 28 is biased away from the. frame 44 and therefore subjects the plunger 54 to a .compres sive force, in the instantembodiment the flexible element 28 is biased toward the frame I20. The

frame is provided at its upper extremitywith a' roller I22 which engages the cable 28, and is provided at its lower extremity with a clamp I24 which may be similar in 'all respects to the clamp 52 of l the previously described embodiment. Intermediate theroller I22 and the clamp I24 the:

cable is engaged by a roller I26 mounted on a pin I28 extending through aligned holes in. the bifurcations Itt of a clevis I32. The clevis is: provided with a threaded bore I34 which is en-. gaged by the threaded extremity, of a shankISS.

A flange I38 formed on the shank I36 intermedi I ate its ends provides a shoulder I40 which en.-'

gages an opposed internal shoulder I42 on the cylindrical sleeve I44. The sleeve I44 is ex ternally threaded at one end as indicated at I46 for securing it to the frame- I20, it being notedthat the internal shoulder I42 is formed on the sleeve at the end thereof remote from the threaded connection. The sleeve I44 is provided through the hollow interior of the sleeve I44 and is provided at its outer end with a wrench head I54 by which the shank may be rotatedto thread it into the bore I34 in the clevis I32. The interengagement at I56 of the adjacent ends and'of the clevis I32 and thesleeve'l44 provides a posi-' tive predetermined amount of flexing of the cable 28 and thus assures a constant ratio between the tension in the-cable and the lateral force exerted on the clevis I32 by the deflected portion of the cable. A lock-screw I 58 may be provided if desired, tolockthe shank I 36 against rotation relative to the sleeve I44.

.T s e e n in al t em odi n 

